Rewrite those record books, because SpaceX has successfully launched its 21st rocket of the year – smashing its previous record, and launching its first national security mission in the process.

At 8.51am Eastern time today, Sunday December 23, a Falcon 9 rocket lifted off from Cape Canaveral in Florida with a shiny new GPS 3 satellite built by Lockheed Martin for the US Air Force. The launch had been delayed several times this week, but finally took off today.

This was the 20th flight of a Falcon 9 rocket this year, and SpaceX’s 21st flight in total, with the other being the Falcon Heavy launch in February. Their previous record was 18 launches in 2017.

This launch did not attempt a landing, unlike SpaceX's recent launches including the somewhat botched attempt earlier this month. There was no landing attempt on this flight because the full performance of the rocket was needed to take the satellite on board to its intended orbit about 2,000 kilometers (1,200 miles) above Earth.

The launch has been heralded as a big success for SpaceX in breaking into the military space market. In 2014, they contested a US Air Force decision to award a non-compete contract to the United Launch Alliance (ULA) partnership between Boeing and Lockheed. The suit was dropped in 2015 when the Air Force opened up the bidding to competition.

And ultimately that proved great for SpaceX. In 2016 they were awarded an $83 million contract to launch this satellite, which itself is worth half a billion dollars. This is the first of a class of new GPS satellites that are being built by Lockheed Martin.

The launch was originally scheduled for May 2018, but was delayed as SpaceX continued testing of its new Block 5 rocket. SpaceX is contracted to fly four more GPS satellites, in deals totaling more than $380 million.

The goal of this satellite, nicknamed Vespucci and which has a lifespan of 15 years, will be to replace an existing old GPS satellite that’s been in orbit since 1997. This new satellite boasts some advanced capabilities over its predecessor, including more secure and accurate signals that are harder to jam.

Ultimately these new GPS 3 satellites will replace all of the 32 GPS satellites operated by the US military in space. Used by an estimated 4 billion people worldwide, these provide us with incredibly useful location data, as well as being used by the military. These new satellites also boast improved integration with Europe's own version of GPS, called Galileo.

Lockheed is also touting an ability to increase the accuracy of GPS receivers such as your smartphone from between three and ten meters (ten and 33 feet) to one and three meters (three and ten feet). However, a complex ground control system built by US defense contractor Raytheon called OCX that’s needed for this capability won’t be ready until 2022 at the earliest, so us civilians won’t see this improvement until then.

While the Air Force might be having a few problems, this launch rounds out a hugely successful year for SpaceX. It got off to a flying start with two launches in January, before that incredible Falcon Heavy launch on February 6. More than half of the 21 launches this year included successful ground landings.

But 2019 could be an even better year for SpaceX. Alongside a string of planned launches, including at least one more Falcon Heavy, the company plans to conduct an uncrewed test flight of its new Crew Dragon vehicle in January. If all goes to plan, they could start launching astronauts by summer 2019.

So while 2018 was undoubtedly a great year for SpaceX, the best is yet to come. And that's saying something.